The biochemical signaling mechanisms underlying the sustenance and perpetuation of long-lasting, experience-dependent functional change in the CNS remain mysterious. Although several appealing potential mechanisms in this context have been identified, including CaMKII autophosphorylation, PKM-zeta production, and AMPA receptor auto-regulation, transcription-regulating mechanisms have received little attention to date. This Project will investigate the hypothesis that a potent transcription-regulating mechanism, altered DNA methylation, might serve as a lasting signal in the hippocampus and cortex to subserve persisting alterations in gene expression, cellular properties, and circuit function. We will test this idea by executing two Specific Aims that test important predictions of the concept. In Specific Aim 1 we will test the hypothesis that DNA methylation controls arc gene expression and hippocampal place field stability in vivo. Prior results have demonstrated that application of a variety of DNMT inhibitors, and conditional deletion of the DNMT 1 and 3A genes, leads to deficits in hippocampal LTP and deficits in hippocampus-dependent long-term contextual learning. However, it is not known how the deficits in hippocampal plasticity lead to memory deficits in the behaving animal. In this Aim we will investigate the role of DNA methylation at the cellular and systems level by investigating experience-driven long-term and short-term changes in DNA methylation in specific hippocampal neuronal subtypes using both immunohistochemistry and laser-capture dissection. In additional studies we will investigate the capacity of DNA methylation to regulate hippocampal arc gene expression, and by investigating the capacity of DNA methylation to control the formation and stabilization of hippocampal place cell firing patterns. In Specific Aim 2 we will test the hypothesis that DNA methylation controls the storage of remote memory in the anterior cingulate cortex. Recent work from several laboratories has demonstrated that remote, i.e. very long-lasting, contextual memories are consolidated and stored in the anterior cingulate cortex. It is intriguing to consider that lasting changes in DNA methylation might contribute to stabilization of remote memory in the cortex, and in this Aim we will test whether remote memory formation is associated with altered DNA methylation in the anterior cingulate cortex, and whether disrupting cortical DNA methylation leads to remote memory destabilization.